The famous double-helix staircase by Leonardo Da Vinci.The spectacular double-helix open staircase that is the centerpiece of the château of Chambord (France). The two helices ascend the three floors without ever meeting.

Threeding.com is a marketplace for free and paid 3D printing models and files.
On our online platform individuals and businesses can buy, sell or just exchange freely 3D model suitable for 3D printing.